The invention relates to a semiconductor substrate, a semiconductor chip and a semiconductor component with areas composed of a stressed monocrystalline material, and to a method for production of a semiconductor component such as this.
Layers composed of stressed silicon are used in semiconductor technology in order to achieve shorter switching times for semiconductor components. Stressed silicon has a distorted crystal lattice with a different lattice constant to that of relaxed silicon. The multiple degeneracy of the valence band minima in the relaxed state is overcome, so that the effective mass of the charge carriers, which contributes to the current flow, falls, and their mobility thus increases. This effect can be used to shorten the switching times of a semiconductor component.
Stressed silicon is conventionally produced by growing silicon layers onto SiGe layers. Conversely, it is also possible to produce stressed SiGe layers on relaxed Si. Germanium has the same crystal structure as silicon, but a lattice constant that is 4.2% greater. When a silicon layer is epitaxially grown on an SiGe layer, lattice mismatches in the silicon lead to the desired stresses.
However, epitaxy cannot be used to produce silicon layers of any desired thickness and with any desired stress magnitude. Beyond a thickness of a plurality of layers or beyond a germanium component of more than 20% in the SiGe layer, stresses are dissipated by the formation of displacements which lead to undesirable scattering effects, or else the layers which are formed are metastable, so that displacements occur when the material is heated in subsequent processes. Epitaxial growing of silicon onto SiGe can thus achieve only restricted stressing of the silicon, with a limited layer thickness.
For these and other reasons, there is a need for the present invention.